Monomeric and Dimeric units of the tandem repeats of the highly reiterated DNA of the African green monkey (C. aethiops) called alpha-component have been cloned in an E. coli plasmid system. The primary nucleotide structure of several such units has been determined. No two repeat units that have been sequenced are identical indicating that alpha-component is made up of a large number of slightly different but closely related sequences. In addition, fragments of the monkey genome of about 17,000 base pairs in length have been cloned in a lambda system. The "library" was screened for segments containing alpha-component. Analysis of a selected group of the recombinant bacteriophage by restriction endonuclease digestion and hybridization reveals that no two are alike. Some of the cloned segments are largely repeats of alpha-component monomer. Other clones have stretches of non alpha-component sequence attached to the highly repeated sequence.